How To Set Up Customized Fictional League?

I would like to set up a 16-team customized league using the fictional teams that come with the game. However, I would like to use different teams than those included with the default 16 team league. I go into the Default.dat file and change the 16 team league table to change to the new teams that I want (note that these teams are part of the game's default 30-team fictional universe). When I go to start my fictional league, the teams haven't changed to those I changed in the default.dat file.
I know that I can manually change the names, etc. but the problem is that you end up having different logos, court graphics, d-league affiliates, owners, etc.
Basically, I like the fictional universe included, all I'm trying to do is change those starting teams for a 16-team league.
Is there a way to edit the default.dat (or another file) so that I can do this? I don't want to edit all the logos, graphics, affiliated teams, etc. manually within the game, I want to do it via the .dat file.
Thanks!
I know that I can manually change the names, etc. but the problem is that you end up having different logos, court graphics, d-league affiliates, owners, etc.
Basically, I like the fictional universe included, all I'm trying to do is change those starting teams for a 16-team league.
Is there a way to edit the default.dat (or another file) so that I can do this? I don't want to edit all the logos, graphics, affiliated teams, etc. manually within the game, I want to do it via the .dat file.
Thanks!